This invention relates generally to a power source device and, to more particularly, a power source device effectively applicable to an electronic image forming apparatus such as an electronic copying apparatus, electronic printer or the like which requires two kinds of power sources, a lower voltage source and a higher voltage source.
In this type of electronic image forming apparatus, the lower voltage source for sequence control and the higher voltage source for power supply to a charger are correlated with each other in such a manner that AC power from a commercially available AC power source is converted, through a lower voltage transformer and a rectifying circuit, into DC power of lower voltage which is on one hand supplied to a sequence control circuit, lamp, solenoid or the like and is on the other hand supplied to the primary winding of a higher voltage transformer of the higher voltage source for charger power supply. In such an arrangement, the higher voltage output is limited because of the duplex restriction by both the conversion efficiency in the lower voltage source and the conversion efficiency in the higher voltage source, and therefore, the energy efficiency is remarkably degraded. Further, such an arrangement requires duplicate driving circuits for the lower voltage transformer and the higher voltage transformer, which leads to an increase in the number of parts and bulkiness of the power source device as well as in the manufacturing cost.